Method of driving a plasma display apparatus

ABSTRACT

A method of driving a PDP apparatus to sufficiently suppress the background light emission and improve the dark room contrast, in which first electrodes and second electrodes are arranged adjacently by turns, a first display line is formed between one side of the second electrode and the first electrode adjacent thereto, a second display line is formed between the other side of the second electrode and the first electrode adjacent thereto, and the interlaced display that displays the first display line and the second display line alternately in different fields is performed, has been disclosed, wherein the reset voltage that directly relates to the intensity of the background light emission is varied according to the number of times of sustain discharges, the display conditions, and so on, in each subfield and the reset discharge is caused to occur with the minimum voltage in each subfield.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of application Ser. No.10/080,410, filed Feb. 25, 2002, and now U.S. Pat. No. 6,809,708.

This application is based upon and claims the priority of Japaneseapplication no. 2001-240662, filed Aug. 8, 2001, and U.S. patentapplication Ser. No. 10/080,410, filed Feb. 25, 2002, the contents beingincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a plasma display (PDP) apparatus and adriving method thereof. More particularly, the present invention relatesto a POP apparatus employing the ALIS (Alternate Lighting of Surfaces)method in which display lines are formed on both sides of each sustaindischarge electrode and an interlaced display is attained, and a drivingmethod thereof.

In Japanese Patent No. 2801893, a PDP apparatus employing the ALISmethod, that can realize a display of high resolution at a low cost, hasbeen disclosed. FIG.1 is a block diagram that shows the rough structureof the PDP apparatus employing the ALIS method disclosed in thedocument. As shown schematically, the PDP apparatus employing the ALISmethod comprises a panel 1 in which first electrodes (X electrodes) X-1,X-2, . . . and second electrodes (Y electrodes) Y-1, Y-2, . . . , thatconstitute the sustain discharge electrodes, and address electrodes A-1,A-2, . . . , a control circuit 11, an address driver 13, a scan driver12, an odd-numbered Y sustain discharge circuit 16, an even-numbered Ysustain discharge circuit 17, an odd-numbered sustain discharge circuit14, an even-numbered X sustain discharge circuit 15, and a power supplycircuit 18 are provided. Since it is disclosed in Japanese Patent No.2001893, detailed description of the structure and operation of eachelement is omitted here.

The ALIS method is characterized by the interlaced display in which afirst display line is formed between each Y electrode and the Xelectrode that is adjacent upward thereto, a second display line isformed between each Y electrode and the X electrode that is adjacentdownward thereto, the first display line is displayed by odd-numberedfields, and the second display line is displayed by even-numbered fieldsand also characterized in that the number of display lines can bedoubled with the same numbers of the X electrodes and the Y electrodesdue to this characteristic and a much finer resolution can be attained.

For a PDP apparatus, various techniques have been proposed to improvethe display quality and reliability, to reduce power consumption, toreduce in cost, and so on. The present invention relates to the resetoperation and, as for this technique, for example, in JapaneseUnexamined Patent Publication (Kokai) No. 2000-75835, the technique toimprove the contrast by utilizing the reset pulse that has a voltagewaveform of a gradual slope in the panel employing the ALIS method hasbeen disclosed. Also in Japanese Unexamined Patent Publication (Kokai)No. 2000-501199, the reset method that utilizes a ramp wave has beendisclosed. Furthermore, in Japanese Unexamined Patent Publication(Kokai) No.2000-242224, the technique, in which the reset pulseaccompanied by lighting of all the display cells is applied only to thefirst subfield to improve the contrast, has been disclosed. Stillfurthermore, in Japanese Unexamined Patent Publication (Kokai)No.2000-29431, the technique, in which operations can be made stable bychanging the reset voltage according to the ratio of light emissionpixels in the subfield, has been disclosed, and in Japanese UnexaminedPatent Publication (Kokai) No. 2000-172224, the technique, in whichmalfunctions can be suppressed by setting the voltage of the reset pulseaccording to the number of times of the sustain discharges in theimmediately previous subfield, has been disclosed.

Recently, the display performance of the PDP apparatus has considerablyimproved and a performance almost the same as that of the CRT can beobtained with respect to luminance, resolution, contrast, and so on. Asthe broadcasting and the video software develop, however, furtherimprovement is expected on the part of the display apparatus, and thedark room contrast is also required to improve further. The luminance ofthe black display, which causes the darkroom contrast to degrade, is theresult of the light emission of the reset discharge needed to stabilizedischarge, therefore, it has been necessary to cause a reset dischargeto occur sufficiently in order to perform addressing of many displaylines at a high speed, and the discharge has been needed to have aluminance of a certain level. As described above, stable operations andthe dark room contrast are in the relationship of trade-off. Accordingto the above-mentioned Japanese Unexamined Patent Publication (Kokai)No. 2000-242224, the background light emission (black luminance) isconsiderably reduced and the darkroom contrast improved by applying thereset pulse accompanied by lighting of all of the display cells once inone field, that is, only in one subfield, and by carrying out the erasedischarge only in the display cells that were lit in the previoussubfield, for the other subfields.

On the other hand, in the PDP apparatus employing the ALIS methoddisclosed in Japanese Patent No. 2801893, a dark room contrast of about500:1 can be obtained by utilizing the reset pulse of the slope-shapedwaveform disclosed in Japanese Unexamined Patent Publication (Kokai) No.2000-75835. In this method, however, the reset discharge for all of thedisplay cells is carried out in every subfield and, therefore, theluminance becomes about ten times as high as that of the backgroundlight emission when the technique disclosed in Japanese UnexaminedPatent Publication (Kokai) No. 2000-242224 is applied. In a panel or ahigh-resolution panel that employs a method such as the ALIS method inwhich every gap between every pair of adjacent electrodes is used as adisplay line, the coupling between two adjacent display cells verticallyapart is strong and it may easily happen that charges diffuse from a litcell to an unlit cell. As a result, the condition of a display cell isaltered even though the address discharge or the sustain discharge isnot carried out after resetting. It has been necessary, therefore, tocarry out the reset discharge for all of the display cells, includingunlit cells, in order to be able to stably perform the address dischargein the next subfield.

FIG. 2A through FIG. 2D show the diffusion of charges to the adjacentdisplay cells due to the sustain discharge in a panel employing the ALISmethod. In the structure of the panel employing the ALIS method, sustainelectrodes (X electrode, Y electrode) are equally spaced, and dischargeis possible in any gap between all pairs of adjacent electrodes. In thefigures, the action when a lit cell is formed between the X2 electrodeand the Y2 electrode in an odd-numbered field is illustrated. FIG. 2Ashows the sustain discharge period in the initial stage. The chargedparticles such as electrons or positive ions generated by discharge movewithin the discharge space by the force of electric field. In a panel ora high-resolution panel employing the ALIS method, the electrode of theadjacent cell exists in the vicinity of the lit cell and a strong forceof electric field is applied thereto, therefore, charges are apt to moveand accumulate thereon. In this case, the charges that diffuse to theadjacent cells are, in most cases, electrons that have a high mobility.

FIG. 2B shows the sustain discharge period in the latter stage of asubfield in which sustain discharge is repeatedly caused to occur, thatis, the number of sustain discharge pulses is large (the sustaindischarge period is long). When the process moves to the next subfield,if resetting (erasing) is performed only for lit cells as disclosed inJapanese Unexamined Patent Publication (Kokai) 2000-242224, charges inan unlit cell contiguous to a lit cell remain intact. In such a state,if the address period is entered and a scan pulse is applied to the Y1electrode as shown in FIG. 2C, the voltage −170V of the scan pulse isoverlapped by the voltage due to the negative charges accumulated on theY1 electrode. Therefore, an address pulse is not applied to an unlitcell and a discharge is caused to occur between the X electrode and theY electrode in a display cell without a discharge between the addresselectrode A and the Y electrode. This display cell is to emit light inthe next sustain discharge period, resulting in an erroneous display.When negative charges are accumulated on the X3 electrode as shown inFIG. 2D, a scan pulse is applied to the Y3 electrode and, even if anaddress pulse is applied to the address electrode A to cause a dischargeto occur between the Y3 electrode and the address electrode, nodischarge is caused to occur between the X electrode and the Y electrodebecause the negative charges on the X electrode side lower the effectivevoltage, therefore, no sustain discharge is caused to occur because wallcharges, necessary for the sustain discharge, are not formed. In otherwords, the cell is not lit.

As describe above, in such a panel employing the ALIS method, in whichthe electrodes of adjacent cells exist very closely, a reset dischargeaimed at all the display cells of each subfield has been indispensable.Moreover, the reset voltage has been specified, a case in which theaccumulated discharges are maximum being taken into account, andresetting has been performed with the voltage in all the subfields.Therefore, the reset voltage has been high and an improvement in thedark room contrast has not been sufficient because it is difficult toreduce the background light emission to below a certain level.

SUMMARY OF THE INVENTION

The present invention aims to solve these problems and the object is torealize a driving method of a PDP apparatus and a PDP apparatus that cansufficiently reduce the background light emission and further improvethe dark room contrast even for a panel employing the ALIS method, inwhich the electrodes of adjacent cells exist closely.

In order to realize the above-mentioned object, in the presentinvention, the reset voltage that directly relates to the intensity ofthe background light emission can be altered according to the number oftimes of sustain discharges or the display state of each subfield. Inthis way, it is possible to improve the darkroom contrast by suppressingthe background light emission, compared to a conventional way, becausethe reset discharge is caused to occur with the minimum voltage for eachsubfield. In concrete terms, the reset period first comprises a firsterase period in which the wall charges of a display cell that was lit inthe previous subfield are erased, secondly a write period in which adischarge is caused to occur for all the display cells to form the wallcharges, and finally a second erase period in which all or part of thewall charges are erased again by a discharge, and the final voltage inthe write period is adjusted.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the invention will be more clearlyunderstood from the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a block diagram that shows the rough structure of the plasmadisplay apparatus (PDP apparatus) employing the ALIS method.

FIG. 2A through FIG. 2D are diagrams that illustrate the problemsrelating to the conventional techniques.

FIG. 3 is a diagram that shows the drive waveforms in the embodiments ofthe present invention.

FIG. 4 is a diagram that shows the reset waveforms in the embodiments.

FIG. 5 is a diagram that shows the structure of the sustain electrodedrive circuit in the embodiments.

FIG. 6 is a diagram that shows the reset waveforms in each subfield inthe first embodiment of the present invention.

FIG. 7 is a diagram that shows the reset waveforms in each subfield inthe second embodiment of the present invention.

FIG. 8 is a diagram that shows the structure of the sustain electrodedrive circuit in the third embodiment of the present invention.

FIG. 9 is a diagram that shows the reset waveforms in each subfield inthe third embodiment.

FIG. 10 is a diagram that shows the effects of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the present invention are described below, withexample cases in which the present invention is applied to a PDPapparatus, employing the ALIS method disclosed in Japanese Patent No.2001893, which has the structure as shown in FIG. 1.

FIG. 3 is a diagram that shows the drive waveforms in the odd-numberedfield of the PDP apparatus in the embodiments of the present invention.The present invention is characterized by the drive waveforms in thereset period, while the address period and the sustain discharge periodare the same as conventional ones, therefore, a description thereof isomitted here and the voltage waveforms in the reset period are describedbelow.

FIG. 4 is a diagram that shows the voltage waveforms to be applied tothe X electrode and the Y electrode in the reset period in theembodiments of the present invention. In the reset period, a pulse of agradual-slope-shaped waveform that gradually reaches −Vwx (−120V) isapplied to the X electrode. The use of such a waveform erases the wallcharges in the display cell that was lit in the previous subfield. Thisis the first erase period. Next, in the state in which the voltage ofthe X electrode is maintained, a pulse with a slope-shaped waveform isapplied to the Y electrode and wall charges are formed by causing adischarge to occur in all of the display cells. This is the writeperiod. Then, in the state in which the voltage Vx (90V) is beingapplied to the X electrode, a pulse of a slope-shaped waveform thatreaches −Vey (−160V) is applied to the Y electrode. This is the seconderase period.

The present invention is characterized in that a voltage, which isapplied to the X electrode and the Y electrode in the first erase periodand the write period, is adjusted. As shown in FIG. 4, the voltage to beapplied has a slope-shaped waveform that gradually changes, therefore,adjusting the voltage means adjusting the voltage level to be appliedfinally. There are three methods of adjusting the voltage: a method ofadjusting the voltage on the Y electrode side, a method of adjusting thevoltage on the X electrode side, and a method of adjusting both. In FIG.4, the final voltage, at which the slope-shaped waveform, to be appliedto the X electrode, arrives varies between −Vwx1 and −Vwx2, and that atwhich the slope-shaped waveform, to be applied to the Y electrode,arrives varies between Vw1 and Vw2. The voltage −Vwx2 is −120V, which isthe same as the conventional one, −Vwx1 is −50V, and the voltage in eachsubfield is set to a fixed value within this range. The voltage Vw2 is200V, which is the same as the conventional one, Vw1 is 100V, and afixed value is set within this range according to the condition of thesubfield and the display state.

FIG. 5 is a diagram that shows the structure of the drive circuit thatproduces the reset waveforms as mentioned above, and the structurecorresponds to the parts of the odd-numbered X sustain circuit 14, theeven-numbered X sustain circuit 15, the odd-numbered Y sustain circuit16, and the even-numbered Y sustain circuit 17 in FIG. 1. Referencenumber 31 refers to a circuit that generates a sustain discharge pulseto be applied to the X electrode, and reference number 41 refers to acircuit that generates a sustain discharge pulse to be applied to the Yelectrode. In this drive circuit, four kinds of voltage values forresetting are prepared in advance for the X electrode side and the Yelectrode side, respectively. The voltage to be applied to the Yelectrode of a display cell 21 in the panel 1 is selected by selectivelyturning on one of switches 42 to 45 corresponding to the voltage value.The power supply of the lowest (the absolute value is the greatest)voltage −Vwx is provided for the X electrode side and a switch 35 isturned on while a switch 37 is maintained on to select the voltage. Toselect a voltage greater (the absolute value is less) than that, aswitch 38 or a switch 39 is turned on while the switch 37 is maintainedoff, or the switch 35 is turned on while both the switches 38 and 39 aremaintained off. When the switch 37 is turned on, the voltage −Vwx issent to the X electrode of the display cell 21 in the panel 1, andotherwise a voltage, which is obtained by subtracting the voltagedetermined by one to three Zener diodes from the voltage −Vwx, is sent.In the present embodiment, the Y electrode side generates the outputvoltage from plural power supplies and the X electrode side generatesthe output voltage from a single power supply utilizing Zener diodes,but it is possible to employ either one method for both the X electrodeside and the Y electrode side at the same time. In the presentembodiment, there are only four kinds of voltage values for the outputvoltage, but this is enough to suppress the background light emissionsufficiently.

FIG. 6 is a diagram that shows the reset waveforms in each subfield inthe first embodiment of the present invention. Since the PDP apparatuscan only light to emit or not, the display of gray level is attained bycomposing each field by plural subfields and combining the subfields tobe lit. In the first embodiment, one field (odd-numbered field oreven-numbered field) is composed of 10 subfields and the sustaindischarge periods of the first subfield and the tenth subfield are thelongest and brightest because the number of the sustain discharge pulsesis the greatest. The nearer the center, the shorter the sustaindischarge period of the subfield is. This is the display sequence tosuppress the color false contour that is an image quality degradationphenomenon inherent to the PDP apparatus.

In the first embodiment, only the voltage Vw, which is applied to the Yelectrode in the write period of the reset period, is made variable andthis voltage is referred to as the reset voltage. In the firstembodiment, the reset voltage in the first subfield is made greatest forthe reasons described below. The first reason is that it is necessary tomaintain active the side of a pair of electrodes that were not lit inthe previous field, because the display of odd-numbered rows and that ofeven-numbered rows are switched in the first subfield in the ALISmethod. The second reason is that since the period of each field issynchronized with the vertical synchronization signal entered from theoutside of the display apparatus, it is necessary to generate spacecharges by causing a comparably strong discharge to occur in advance inall of the display cells when the video signal has a long period of thevertical synchronization signal, because the interval between thecompletion of the final subfield and the inception of the first subfieldis lengthened and the priming effect that affects the stability ofdischarge is degraded. The third reason is that since the number oftimes of the sustain discharge in the tenth subfield is large, it mayhappen that many electrons have accumulated in the adjacent cells asshown in FIG. 2(B), therefore a high voltage is required, for example,because the electrons accumulated on the Y electrode side lower theeffective value of the reset voltage (Vw). For the reasons describedabove, it is necessary to set the reset voltage in the first subfield toabout 200 V. Conventionally, the voltage of 200 V was an excessiveapplied voltage in the subfields other than the first subfield becausethe voltage was applied to all the subfields.

The reset voltage in the second subfield can be lowered to below that ofthe first subfield because the first and the second reasons describedabove no longer exist, although the number of times of the sustaindischarges in the immediately previous first subfield is large.

The number of times of the sustain discharges in the fifth subfield isthe least, and is only a few times, and there are few chargesaccumulated in the adjacent display cells as described in FIG. 2,therefore, the state established in the previous reset period ismaintained even in an unlit cell contiguous to a lit cell. Therefore,the reset voltage of the subsequent sixth subfield is set to the leastvoltage, and to about 100 V. Since the discharge threshold voltagebetween the X electrode and the Y electrode is about 220 V, a dischargeis seldom caused to occur in an unlit cell.

The reset voltages of the third subfield through the fifth subfield arebetween the reset voltage of the second subfield and that of the sixthsubfield, and the reset voltages of the seventh subfield through thetenth subfield are set to those which are slightly greater than that ofthe sixth subfield because the length of the sustain discharge periodgradually increases. The length of the reset period is fixed in thefirst embodiment.

FIG. 7 is a diagram that shows the reset waveforms in each subfield inthe second embodiment of the present invention. The differences from thefirst embodiment shown in FIG. 6 are that not only the voltage Vw to beapplied to the Y electrode is varied but also the voltage to be appliedto the electrode is varied according to various conditions. The absolutevalues of the voltage to be applied to the X electrode in the firsterase period and that to be applied to the Y electrode in the writeperiod of the reset period in the first subfield are made large for thesame reasons as those described above. Although the reset voltage in thefirst subfield is made low in the first embodiment, the absolute valueof the voltage on the X electrode side is made less (actually greaterbecause it is a negative voltage) in the second embodiment, while thevoltage to be applied to the Y electrode is maintained high. The reasonis described below. On the average, the address electrode becomes acathode in the sustain discharge period therefore the negative chargesformed by the address discharge on the address electrode side areexposed to the sustain discharge and gradually erased. If, however, thenumber of times of the sustain discharges is small, they are hard toerase. It is not preferable for the charges to remain because they wouldact to lower the effective value of the address pulse voltage.Therefore, in order to erase the negative charges on the addresselectrode side in the reset period, the voltage between the Y electrodeand the address electrode is set so as to be large even though thatbetween the X electrode and the Y electrode is set so as to be low anderasing the negative charges on the address electrode side is promotedby the discharge between the address electrode and the Y electrode.

FIG. 8 is a diagram that shows the structure of the sustain electrodedrive circuit in the third embodiment of the present invention. In thedrive circuit in the first and the second embodiments shown in FIG. 5,the output voltages are generated by providing plural power supplies ofdifferent voltages or utilizing the Zener diodes with the single powersupply, but the drive circuit in the third embodiment differs in thatthe voltage to be applied to the electrode is gradually varied and theapplication of voltage is terminated when a fixed value is reached bymonitoring the voltage of the electrode. It is assumed that an Xelectrode side drive circuit 30 has the same structure as that of the Xelectrode side drive circuit shown in FIG. 8. The reset voltage Vw isapplied to the Y electrode of a display cell 21 via a current limiter 55by turning a switch 54 on. Because the current limiter 55 is provided,the current that enters the panel 1 is limited and the voltage of the Yelectrode varies with a gradual-slope-shaped waveform. Moreover, thereset pulse voltage to be applied to the Y electrode is monitored by avoltage detector 56 and the switch 54 is turned off by a reset voltagecontrol circuit 53 when a fixed voltage is reached. The reset voltagecontrol circuit 53 receives information such as of a subfield inoperation and about the number of times of the sustain discharges from adisplay sequence control circuit 51 and determines the reset voltage tobe applied based on this information.

In the third embodiment, at the same time as the switch 54 is turned offwhen the reset voltage reaches a fixed value, the next erase process isinitiated. FIG. 9 is a diagram that shows the reset waveforms in eachsubfield in the third embodiment. Although the voltages of the Yelectrodes are maintained for a while after reaching each fixed value asshown in FIG. 6 and FIG. 7, respectively, the application of voltage isterminated immediately after the voltages of the Y electrode reach eachfixed voltage, respectively, in the third embodiment and the action ofthe next erase period is initiated. This will reduce the operating timeand the saved time can be used, for example, to lengthen the sustaindischarge period.

The first through third embodiments are described above, and it isneedless to say that the optimum values are set for each voltage andoutput voltage according to the panel design or drive conditions.

FIG. 10 is a diagram that illustrates the effects of the presentinvention, comparing the intensity of the reset light emission, when thereset voltage in each subfield is controlled so as to be optimum asshown in the first through the third embodiments, to that of theconventional art. As shown schematically, the light emission intensityby the reset pulse is made less in the center, the background luminanceis lowered to about half to one third of the conventional one, and thedarkroom contrast is doubled or tripled.

As described above, the main reason is that the charges generated by thedischarge diffuse and accumulate on the electrodes of the adjacentdisplay cells when the number of times of the sustain discharges islarge. Therefore, when the number of times of the sustain discharges issmall in the previous field, it is possible to lower the reset voltagein the next field. For example, a power increase is limited byshortening the length of the sustain discharge period when the displayratio is high in the PDP apparatus and, in such a case, it is possibleto lower the reset voltage in the write discharge process.

As described above, according to the present invention, the backgroundluminance can be suppressed and the dark room contrast can be improvedbecause it is not necessary to apply an excessively great voltage forthe reset discharge in each subfield.

1. A method of driving a plasma display apparatus having firstelectrodes and second electrodes extending in a first direction andarranged adjacently by turns, wherein each display field comprisessubfields, and each subfield comprises at least one of a reset period,an address period, and a sustain discharge period, and the subfields ineach display field include subfields for a write discharge process thatperforms an entire write discharge, the method comprising: in the writedischarge process for the entire discharge process, applying respectivedifferent voltage levels during the corresponding, different subfieldsof a given field.
 2. The method of driving a plasma display apparatus asset forth in claim 1, wherein the reset period comprises the writedischarge process and an erase discharge process, in the subfields thatperform the entire write discharge, and the write discharge process is aslope-shaped waveform having the voltage level gradually changing in apositive direction and the erase discharge process is a slope-shapedwaveform having the voltage level gradually changing in a negativedirection.
 3. A method of driving a plasma display apparatus havingfirst electrodes and second electrodes extending in a first directionand arranged adjacently by turns and third electrodes extending in adirection perpendicular to the first direction, wherein each displayfield comprises subfields, and each subfield comprises a reset period,an address period, and a sustain discharge period, comprising: in thereset period, executing a write discharge process and an erase dischargeprocess, wherein a voltage waveform in the write discharge process is aslope-shaped waveform, a voltage of which gradually changes, and in thewrite discharge process, at least one subfield comprising a voltagedifferent from the other subfields.
 4. A method of driving a plasmadisplay apparatus, as set forth in claim 3, wherein, in the writedischarge process, the voltage to be applied to the first electrode orthat to be applied to the second electrode, or that to be applied toboth is varied and a fixed voltage is applied to the third electrode. 5.A method of driving a plasma display apparatus, as set forth in claim 3,wherein a period of the write discharge process is constant and thevoltage is maintained until a completion of the write discharge process,after a reference voltage is reached in each subfield.
 6. A method ofdriving a plasma display apparatus, as set forth in claim 3, wherein arate of change of the voltage of the voltage waveform in the writedischarge process is the same in each of the subfields and erasedischarge process is performed immediately after the voltage in thewrite discharge process reaches a reference voltage.
 7. A plasma displayapparatus having first electrodes and second electrodes extending in afirst direction and arranged adjacently by turns, third electrodesextending in a direction perpendicular to the first direction, whereineach display field comprises subfields, and each subfield comprises areset period, an address period, and a sustain discharge period, theplasma display apparatus comprising: a drive circuit applying a drivevoltage to the first and the second electrodes, and, in the writedischarge process, outputting a voltage, for at least one subfield,different from voltages of the other subfields, wherein in the resetperiod, a write discharge process and an erase discharge process areexecuted, and a voltage waveform in the write discharge process is aslope-shaped waveform, a voltage of which gradually changes.
 8. A plasmadisplay apparatus, as set forth in claim 7, wherein the drive circuitcomprises: plural power supplies for the write discharge process and thevoltage during the write discharge process is determined by a selectionof a power supply from the plural power supplies.
 9. A plasma displayapparatus, as set forth in claim 7, wherein the drive circuit comprises:a voltage source circuit in which the voltage gradually increases to areference value as time elapses, and a voltage monitor circuit thatmonitors the voltage to be applied to the first and second electrodes,and the application of the voltage is interrupted when the voltage tothe first and second electrodes reaches the reference value.